Java project base converter net beans help

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Java

I have a programming assignment (in java, I use net beans dos to write this). This assignment needs to show the binary conversion as listed within the code. The issue is, the output displays the Base 2, Base 5, Base 7, and Base 8 conversions backwards/ in the wrong order and gives a weird long dialog message (PLEASE TEST THIS IN NETBEANS FIRST SO YOU CAN SEE THE ISSUE). So could someone take a look at what I have now, and fix it to where it displays the assignment correctly in the output. Thanks. Please also show the output.

package base.project;
import javax.swing.*;
public class BaseProject {
	public static String output = "";
	private static void convertobase(int n, int i){
		output += "\n the number " + n + " converted to base " + i;
		while (n > 0){
			output += " " + n%i;
			n = n / i;

		}

		output += "\n is " + output;
		JOptionPane.showMessageDialog(null, output);


	}
	public static void main(String[] args) {
		while (true){
			String input = JOptionPane.showInputDialog("enter any integer number \n");
			int n = Integer.parseInt(input);
			String in = JOptionPane.showInputDialog("\n Make the folowing selection"
			+ "\n to convert to decimal number"
			+ "\n2 to conver to base 2"
			+"\n5 to convert to base 5"
			+ "n7 to conver to base 7"
			+ "\n8 to convert to base 8");
			int selection = Integer.parseInt(in);
			switch(selection){
				case 2:
				convertobase(n, 2);
				break;
				case 5:
				convertobase(n, 5);
				break;
				case 7:
				convertobase(n, 7);
				break;
				case 8:
				convertobase(n, 8);
				break;
			}

		}
	}
}

What I have tried:

I have completed the assignment however it's not working properly.